Catalytic conversion process



July 16, 1946. AT, B MccULLoCH 2,404,680

CATALYTIC CONVERSION PROCESS l Vaporiz) QM Z/ZINVENTOR.

ATTORNEY.

July 106, 1946- .'r. B. MccuLLocH CATALYTIC CONVERSION PROCESS Filed oct. 15. 1943 I5 Sheets-Sheet 2 E3 :5am

orwsoo anni l v ATTORNEY,

July 16,1946.

Alkym'fion Reaclor lsomerzorion Reactor T. B. MccuLLocH cATALYTIc CONVERSION PRocEss Filed oct. 15, 1945. A

3 sheets-sheet 's Make-Up Acid g-fWINI/ENTUR.

BY I

ATTORNEY.

Spent Acid Patented July 16, 1946 CATALYTIC CONVERSION PROCESS Thomas B. McCulloch, Baytown, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application october 15, 194.3,V serial No. 506,327

The present invention relates to a method for changing the structural configuration of a parain hydrocarbon. More particularly the invention is concerned with the isomerization of paraffin hydrocarbons and the utilization of the resulting isoparaffin hydrocarbons in the alkylation of olens. In its more specic aspects the invention is concerned with the isomerization of normal parafns to isoparaflins in the presence of sulfuric acid at elevated temperatures followed by the alkylation of the isomerized product with olens, in the presence of the catalyst withdrawn from the isomerization reaction.

It is well known in the prior art to isomerize normal parains to isoparans utilizing an aluminum halide in the presence of a hydrogen halide as the catalyst. It is also known to isomerize isoparafns in the presence of aluminum halides and hydrogen halides and then to utilize the catalyst from the isomerization stage to alkylate the isomerzed product with olefins in an alkylation stage. This latter process, however, has disadvantages in that aluminum halides and hydrogen 9 Claims. (Cl. 260-683.4)

halides are expensive and do not readily lend themselves to recovery and reutilization in the process.

The prior art also teaches the isomerization of selected isoparafns to other isoparains in the presence of hydrogen fluoride and concentrated sulfuric acid. These latter processes have the objection of being limited to the isomerization of one iso-compound to another of similar structure.

Prior to the present invention mention has been made in the literature of the isomerization eiect of sulfuric acid in alkylation reactions. In all of these previous investigations the isomerization noted was the isomerization of one branched chain compound to another of more or less branched nature. In all of these earlier investigations the sulfuric acid employed as the catalytic agent was utilized at relatively low temperatures. However, isomerization of normal parafns to the corresponding isoparans in the presence of sulfuric acid was heretofore unreported.

In the present invention normal parafns are isomerized to isoparains with concentrated sulfuric acid as the catalyst at temperatures substantially above that employed heretofore in the isomerization of isoparans to more or less branched chain hydrocarbons. In its broadest aspects the invention contemplates theisomerization of normally gaseous or normally liquid normal paraffins to the corresponding isoparanins employing concentrated sulfuric acid at temperatures in the range from about 300 F. to about 500 F. The invention also contemplates the isomerization of mixtures of normal parafns occurring in the gasoline boiling ranges. One specific feature of the present invention is the isomerization of normal paranns to isoparafns and the alkylation of the isomerized product with olens utilizing as the catalyst for the alkylation reaction the catalyst withdrawn from the isomerization reaction.

When carrying on the isomerization reaction of the present invention, the normal paraffin is contacted with concentrated sulfuric acid of a strength between 90 and 100 per cent H2SO4. It is preferable that the hydrocarbon be in the vapor phase when it is brought into contact with the sulfuric acid, but liquid phase may also be employed. When the hydrocarbon is in the liqquid phase during the contacting step it is necessary that super atmospheric pressure be employed to maintain the hydrocarbon in liquid form at the temperatures specied.

In isomerizing normal parainns to isoparafns in the presence of concentrated sulfuric acid, the amount ofv acid contacted with the hydrocarbon should be at least equal to the volume of hydrocarbon charged. `In general, however, it is preferred to employ an excess of hot sulfuric acid. The preferred ratios of hot sulfuric acid to hydrocarbon charge will range from about 2:1 to about 5:1.

Since hot sulfuric acid is a powerful oxidizing agent, it is preferred to employ relatively short contact times between the hot acid catalyst and the hydrocarbons. As stated above, it is preferred that the hydrocarbon contacted with the sulfuric acid be in the vapor phase, and under such conditions contact times of less than 15 minutes, and usually less than one minute, are most satisfactory. When the hydrocarbon is maintained in a liquid phase, contact times of up to minutes between the sulfuric acid catalyst and the hydrocarbon may be used.

Since hot sulfuric acid is corrosive toward steel and steel alloys, it is desirable to inhibit hot sulfuric acid against steel and steel alloys by introducing and maintaining in the hot acid catalyst an inhibitor of corrosion. It is well known in the piokling industry when using sulfuric acid as a pickling agent to utilize inhibitors of corrosion, and similar inhibitors may be used in the practice of the present invention.

When it is undesirable to use corrosion inhibitors as a precaution against destruction of metallic equipment, ceramic reactors and handling lines and other auxiliary equipment may be uti- 3 lized. Construction of such equipment does not present any particular problems.

The present invention will be better understood by reference to the drawings in which:

Figure l is a flow diagram of one embodiment of the present invention utilizing 'not sulfuric acid as the catalyst;

Figure 2 is a flow diagram of another embodiment for practicing the present invention in which the product and the catalyst from the isomerization stage are cooled and then charged to an alkylation stage wherein olefins are alkylated with the somerized product; and

Figure 3 is a flow diagram of still another embodiment in which the product and the catalyst from the isomerization stage are cooled, the isomerized product and oleiins being charged directly to an alkylation reactor with recycling of la portion oi the acid catalyst from the alkylation reactor back to the isomerization reactor.

In the several embodiments described with reference to Ythe drawings, it will be assumed for purposes or illustration that normal butane is being isomerized to isobutane in the presence of hot sulfuric acid'oi about 97 per cent concentration at 450 F. It will also be assumed for the purpose of illustration that the normalbutane is maintained in the vapor phase during vthe isomerization reaction.

Referring now to the drawings 'and specically to Figure `1, nmneral I I illustrates a charge tank containing normal butane. Normal butane is withdrawn from tank II by pump 'I2 located in line T3 and passes through vap'orizer Ill where the hydrocarbon is completely vaporized. The vaporizedhydrocarbons are injected through distribution means I5 into isomerization reactor I6 wherein Ythe vaporized hydrocarbons are intimately contacted with hot sulfuric acid descending therein and introduced by way of line I7.

The l.hot sulfuric acid discharged into the upper portion of isomerization reactor Il ows downwardly therein and contacts the upflowing vaporized hydrocarbon. It is understood that isomerization reactor I6 may be a packed tower, a tower equipped with bell caps or any suitable contacting means whereby intimate contact ybetween the vaporize'd normal butane and the hot sulfuricacid may be effected.

Isomerized vproduct leaves isomerization reactor I6 by way of line I8, passes through cooler I9, wherein the product and any acid carried over with the product is cooled and liquefied, and discharges into settler wherein suicient residence time is provided for separation between the hydrocarbon `and acid phases. Line 2| connects tosettler 20 for Aremoval of any SO2 resulting from decomposition of the sulfuric acid catalyst in isomerization reactor I6.

The acid separated from the hydrocarbon phase in settler 2U discharges therefrom by way of line 22 and recycles thereby back to isomerization reactor IG. Between settler 2D and isomerization reactor I6, heat must be introduced tothe withdrawn acid and this is effected by providing acid heater 23. is admixed with acid discharged from reactor I6 by way of line 24 and passes through coil 25 located in acid heater 23 and ultimately discharges, as described before, by way of line II into reactor I6.

Since, for best results, itis necessary to maintain the acid strength between 90 per cent and 100vper cent of H2SO4, a portion of the acid discharged from settler '20 by way of line 22 is with- The Vwithdrawn acid from settler 20' 4 drawn from the system for further treatment as desired by opening valve 26 located in line 2l. When acid is withdrawn from the system, it will be necessary to introduce a like amount of fresh acid to maintain the acid catalyst at maximum eciency. Provision is therefore made for introduction 0f fresh strong acid by opening Valve 28 located in line 29 connecting line 22 with an acid supply source not shown.

Since the isomerized hydrocarbon product separated from the acid in settler 20 may still contain residual acidity, provision is made for removal of acid bodies by washing the hydrocarbon with an alkaline reagent. lTherefore the hydrocarbon phase from settler 20 discharges therefrom by line v3i?, an alkaline reagent is added thereto by line 3| and these components pass into mixer 32. The mixture of alkaline reagent and hydrocarbon discharges from mixer 32 by way of line 33 into Second settler 3d, which is of suicient capacity to provide separation by gravity between the hydrocarbon Vand alkaline reagent phases. The isom-erized product is removed from settler 34 by 4way of line 35 and then may be submitted to distillation for recovery of the isobutane or may be used as such, or further handled as refining practices may dictate,

The alkaline reagent phase separated from the hydrocarbon phase in settler 311 is recycled by way of lines 36 and pump 3l `to contact additional quantities of isomerized product in line 3Q.

In order to maintain the strength of the alkaline reagent at an optimum point for removal of acidic materials, it'will be necessary from time to time to withdraw a quantity of the alkaline reagent by opening valve 38 inline 39. Under these circumstances it will be necessary to introduce an equivalent amount of fresh alkaline reagent by opening valve 139 in line 3|.

With respect to the embodiment shown in Figure 2, a normal butane feed in charge tank 5i) is'introduced by way of line 5i, pump 52, and line 53, Vaporizer 54 and distributor means 55 into isomerizat'ion reactor 55. As described with relationto 'the embodiment of Figure lJ isomerization reactor 56 may be a packed tower, a tower equipped with bell cap plates or any equivalent contacting means whereby contact between vapors and liquids is eifected. AThe vaporized hydrocarbons pass upwardly through isomerization reactor 55 and are contacted with down-flowing hot sulfuric acid introduced thereto by way of line 5l; the hydrocarbons and hot sulfuric acid remain in contact for a time suicient to allow conversion of the normal butane to isobutane. The hydrocarbons pass upwardly and out of isomerization reactor 55 by way of line 53, are cooled and liqueiied on passage through cooler 59 and are discharged into settler .55), which is provided with sufcient capacity to allow separation by gravity of hydrocarbons from entrained catalyst carried over therewith. Settler vSi) is provided with line 5I to lead off anySO2 resulting from decomposition of the sulfuric vacid at the high temperatures employed in reactor 56.

The acid separated from the hydrocarbons in settler Se .discharges therefrom by Way of line 62 and recycles to isomerization reactor y5S by way of line B3 and coil 64 located in acid heater B5, and line 57, as has been described before. The acid Withdrawn from isomerization reactor 56 alsodischarges into line 63 by line 66 for passage through coil 64 :for maintenance of temperature in isomerization reactor 5S and for reutilization in .the process.

' `A branch line 61 equipped with valve 68 connects line 66 with line 62 to allow utilization of a-portion of the acid withdrawn from isomerization reactor 56 as a catalyst in alkylation of the isomerized product, as will be described hereinafter. Line 63 is equipped with a Valve 69 for regulation of flow of acid from settler 60 to reactor 56.

The acid discharged into line 62 by way of lines 66 and'61 from isomerization reactor 56 may be routed toalkylation reactor 19 through line 1I by opening valve 12 located therein. y

The isomerized product separated from the acid carried over therewith in settler 6!)v discharges therefrom by way of line 13 and is introduced in admixture with an alkaline reagent injected into line 1,3 by line 14 into mixer 15 where the alkaline reagent and hydrocarbon phases are intimately contacted for removal of residual acidic material resulting from the contact of the hydrocarbon with the hot sulfuric acid catalyst in reactor 56. The mixture of alkaline reagent and hydrocarbon discharges from mixer 15 by way of line 16 into a second settler 11 wherein provision is made for separation between isomerized hydrocarbon product and the alkaline reagent.

The separated alkaline reagent discharges from settler 11 by way of line 13 and may be recycled therefrom by pump 19 to line 1d for admixture in line 13 with additional quantities of isomerized hydrocarbon product.

Provision is made for withdrawal from time to time of amounts of alkaline reagent by opening Valve 89 located in branch line 8|. When alkaline reagent is withdrawn from the system by line 8l, it will be necessary to introduce an equivalent amount of fresh alkaline reagent by opening valve 3 2 located in line 14.

The hydrocarbon separated from the alkaline reagent in settler 11 discharges therefrom by Way of line 83 and is introduced thereby into separator 64, which, for purposes of illustration, may be a distillation tower. In separator 84 provision is made for separation of isobutane from unreacted normal butane. This is conveniently done by adjustment of temperature and pressure conditions by heating means 85 whereby a fraction consisting essentially of isobutane is removed overhead through line 86 for handling as will be described further. The unreacted normal butane discharges from separator 84 by way of line 53 for re-introduction into isomerization reactor 56 along with fresh feed from tank 50.

The isobutane `taken overhead from separator 84 through line 86 is admixed with olefins introduced therein by way of line 61 and the mixture is discharged into line 1| carrying sulfuric acid from isomerization reactor 56 and settler 60. Prior to contact between the mixture of olens and isobutane with the sulfuric acid, the acid is passed through cooler 88 whereby its temperature is reduced to optimum alkylation temperatures.

The cooled mixture of olens, isobutane, and acid discharges by way of line 1I into alkylation reactor wherein temperature, pressure and other conditions are maintained suitable for alkylation of the isobutane withr the oleiins.

The alkylation stage in the present invention is conventional to the alkylation art and details of its operation will not be gone into herein.

The effluent from the alkylation reactor containing alkylate, unreacted hydrocarbon, and entrained acid catalyst discharges therefrom by way of line 89 into third settler 90 whereina s ep-V aration is made between the hydrocarbon/and acid phases. Provision is made for withdrawing acid from settler 90 by way of line Siland re cycling of a portion of the vwithdrawn acid to line 1i by opening valve 92 located ,in line 9|. Since it will be necessary to maintain the strength of acidused in isomerization reactor 56 and in alkylation reactor 10 at an optimum point for isomerization and alkylation, respectively, it will be necessary to withdraw continuously from the system an amount of spent, acid and to introduce continuously an equivalent amount of make-up acid. The spentV acid may be discharged from the system by opening Valve 93 located in line 94 and make-up acid may be introduced into the system by opening valve .95 located in line 96 connecting line .62 to an acid supply s ource not shown. y

In some instances it may be desirable to introduce make-up acid into vthe system immediately ahead of alkylation reactor 19 instead `of into the acid recycled to isomerization reactor 56, `In those particular instances make-up acid may :be introduced into the system from asource ,not shown by opening valve 99.111 line |00 which connects into line 1 I. It is understood, of course, that when make-up acid is introduced into'line 1I, rather than into line 62, it will be necessary to withdraw used acid from the process by open ing valve IGI in line |02., Likewise, the acid separated in settler-90 from the hydrocarbon containing alkylated product Will in turn be recycled to isomerization reactor 56 by opening valve |03 inline |04.

As conventional in the alkylation art, a portion of the acid emulsion discharged from the bottom of alkylation reactor 90 may be recycled to the system through line 91 and valve 98 located therein. It will be apparent from the foregoing embodiment that it is possible to employ the catalyst from the isomerization reactor for alkylation of the isomerized product. It wil1 be `further apparent that such a system, wherein a cheap reagent like sulfuric acid is utilized, embodies a considerable economic advantage over the conventional art.

With reference to the third embodiment `of the present invention shown in Figure 3, a normal butane fraction from natural gasolineor any other petroleum source is introduced into the system from tank III) by way of lines III, IIZ and pump H3 located therein. The normal butane passing through line II2 is vaporized in Vaporizer IM and is introduced through dis-V tributing means II5 into isomerization reactor H6. In isomerization reactor II6 the vaporized hydrocarbons flow upwardly therein and contact down-flowing hot concentrated sulfuric acid introduced into the upper portion of isomerization reactor H6 by way of line H1. Isomerization reactor IE6 is similar to the isomerization reactors described with respect to Figures 1 and' 2.

In isomerization reactor II6 temperature and other conditions are adjusted for conversion of the normal butane to the isobutane as described hereinbefore..

The product from isomerization reactor II6 consisting of isobutane and unreacted normal butane, discharges therefrom by way of line -I I8 and passesthrough cooler I I9 which reduces the temperature of the hydrocarbon mixture and any entrained acid catalyst to a temperature optimum for alkylation of the isobutane with lolefin in thepresence -of sulfuric acid. -This'temper-V `35" to '7?0' F. The `cooled reacted' hydrocarbon mixture rcontaining entrained acid discharges by way lof line H8, in admixture with olens intron duced by way of line |20 and acid Yinjected by Way of line |2|, into alkyl'ation reactor |22 wherein alkylation between the olens andv isoparains is effected as will be described further.

Hot acid introduced into isomerization reactor |||i vby way of line ||1 fiowsrdownwardly therein contacting the tip-flowing vaporized hydrocarbons, introduced through distributing means I I5. The hot acid flows out of reactor ||6 'by way of line |23 and at least a part of this acid discharges into line |24, which connects to heating coil |251 located in acid heater |26, wherein the temperature of the acid discharged from the isomerization reactor and later stages of the process is adjusted for optimum isomerization of the normal -butane to isobutane.

Valve |40 is provided in line |23 forv regulating the flow of discharged acid from isomerization reactor by way of line |23. The reason for providing valve |48 is to allow circulation of a portion of the discharged acid to the alkylation reactor system through line I2|. This is accomplished by opening valve |21 located in line |2| so that the hot acid may pass through cooler |128 for reduction of temperature of the hot acid to the proper alkylation temperature whereby the acid then admixes with the isomerized product in line 8 as has been previously described.

`The mixture of isobutane, normal butane, oleilns and acid discharges into alkylation reactor |22. The conditions maintained in alkylation reactor |22 are conventional in the alkylation art and will not be described further herein. It is suicient to say that best conditions selected to give optimum alkylation between the isobutane and the oleiins are maintained therein.

`Acid catalyst in an emulsified statewith hydrocarbons is withdrawn from alkylation reactor |22 by Way of line |3I for recycling toreactor |22 through lines |32 and |"2`| connecting to line ||8. From alkylation reactor |22 a mixture of alkylate, unreacted hydrocarbons and entrained acid is discharged by way of line |29 into settler |30.

In settler |30 sufficient residence time is a1- lowed Ifor gravity separation between the hydrocarbon and acid phases. After separation is accomplished, the acid is withdrawn Jfrom settler |30 by Way of line |33 which connects to line |32. and which allows recycling of the acid to the alkylation reactor. necessary to withdraw from the system ar portion of the acid discharged 'from settler v|30 to maintain the acid in the isomerization reactor and in the alkylation reactor at av strength optimum for the reactions. In these instances an amount of the spent acid is withdrawn from the system by opening valve |34.

When spent acid isdischarged from the system it will vbe necessary to add an equivalent amount of make-up acid for maintenance of optimum acid strength. This is accomplished by opening valve |35 located in line |36 connecting to line |24.

Similar to the embodiment described with rrelation to Figure I, it is within the sco-pe of the present invention to yintroduce make-up acid into 'the system so that the fresh Yacid contacts the i-sopara'iin and olefins in alkylation reactor |22. In this particular instance the make-up acid will be introduced into the system by opening valve From time to time it will be a sidered to be one or more distillation zones.

|44 in line |45 connecting to a source of acid storage not shown. Similar to the embodiment of Figure 1 the spent acid will be withdrawn from the acid stream recycling to the isomerization reactor H6. The acid may be discharged from the system by opening valve |46 in line |41.

In some instances it may be desirable to return a part of the acid utilized in the alkylation reaction to the isomerization system. Therefore, provision is made for introduction of the acid withdrawnfrom settler by line |33 into isomerization reactor by opening Valve |31 located in line |24, which connects to isomerization reactor |||i by way of heating coil |25 and line |1. The presence of a small quantity of alkylation acid may be beneficial in the isomerization reaction, since the alkylation acid contains small quantities of the alkyl sulfates. It has been observed, inisomerization of parafin hydrocarbons with sulfuric acid, that the acid becomes colored on use and the theory has been advanced that the isomerization proceeds through the formation of the intermediate olen. This would suggest the formation of alkyl sulfates. Therefore, it is within the scope of this invention to add extraneous alkyl sulfates to the isomerization acid.

The hydrocarbon phase separated from the acid in settler |30 is withdrawn therefrom by line |38, which connects to separator |39. It will be understood, of course, that acidic bodies remaining in the hydrocarbon phase may be removed by treatment with an alkaline reagent. For purposes of illustration separator |39 will be con- In separator |39 temperature and pressure conditions of the hydrocarbon introduced thereto by line |38 are adjusted by heating means |40 to allow separation of an isoparafrin fraction, a normal butane fraction, and an alkylate fraction.

The isoparafn fraction, in general, vinll comprise a minor portion of the stream which was introduced into separator |39 by way of line |38. Since most of the isobutane resulting from isomerization of the normal butane in isomerization reactor H6 will have been consumed in alkylation reactor |22, the remaining isobutane fraction will discharge from separator |30 by way of line. icl and maybe recycled to the alkylation reactor or may be further used as desired. The unreacted normal butane discharged with isob'utane from isomerization reactor H5 will be recovered by line |42 for recycling to the isomerization reactor. Line |42 connects into line i |2 whereby the feed is introduced into isomerization reactor H6.

Alkylate, suitable for inclusion in 100 octane number aviation fue-ls, is withdrawn from separator .by way of line |43 for further treatment and handling. rThe alkylate withdrawn by way of line M3 may be distilled for separation of light and heavy allrylates and caustic washed prior to introduction of light blending agents and tetra-ethyl lead.

While the present invention has been vdescribed and illustrated by the isomerization of normal but-ane and the alkylation of the resulting isobutane, it is to lbe clearly understood that other normal parafnsr such as normal pentane, normal heptane., `normal hexane and the like, may comprise the charge stock of the present process.

The Ynature and objects of the presentinvention `having been completely illustrated andidescri'bed,

what I Wish to claim as new and useful and tosecure by Letters Patent is:

l. The isomerization of normal parains to isoparaiiins comprising the steps of contacting a normal paraiiin hydrocarbon' with sulfuric acid maintained at a temperature in the range oi 300 to 500 F. to cause the isomerization of the normal parairin hydrocarbon and subsequently separating the resulting isomerized hydrocarbon.

2. A process in accordance with claim 1 in which the normal parain hydrocarbon is maintained in the Vapor phase.

3. A process for converting a normal pararn hydrocarbon to an isoparain hydrocarbon which comprises the steps of contacting a normal parafin hydrocarbon in the vapor phase with sulfuric acid at a temperature of between 300 and 500 F. in an isomerization Zone, removing any eliluent including an acid yphase and the hydrocarbon phase from the isomerization Zone, cooling the effluent and separating it into a hydrocarbon phase and an acid phase, heating the separated acid phase and recycling the reheated acid to the isomerization stage and removing acidic constituents from the hydrocarbon phase.

A process in accordance With claim 3 in which the paraffin hydrocarbon is normal butane.

5. A process in accordance With claim 3 in which the normal paraflin hydrocarbon is normal pentane.

6. In the production of high octane number fuels the steps of isomerizing a normal parafn hydrocarbon by contacting it in vapor phase with sulfuric acid at a temperature of between 300 and 500 separating isomerized hydrocarbon product from the hot acid catalyst, cooling the hydrocarbon product and adding oleins thereto, cooling the acid catalyst and mixing it with the hydrocarbon phase containing olens and maintaining the mixture under conditions to cause alkylation of the olens and subsequently recovering an alkylate of high octane number.

'7. A :process in accordance with claim 6 in which the normal parain hydrocarbon is normal butano and the added olens are butylenes.

8. A method for producing alkylate which comprises contacting a normal paraffin in vapor phase With sulfuric acid in an isomerization zone at a temperature of between 300 and 500 F. to cause isomerization of the normal paraiiin, separating the resulting isomerized hydrocarbon product from the acid, mixing olens With the hydrocarbon product, cooling the acid and adding it thereto and maintaining the mixture under conditions to cause alkylation oi hydrocarbons present therein, separating a hydrocarbon phase containing alkylate from an acid phase, recovering isoparaii'lns, normal parains and alkylate from the hydrocarbon phase and recycling at least a portion of the acid phase to the isomerization zone.

9. A process in accordance with claim 8 in which the normal parafiin is vaporized normal 30 butane. 

